“The ink” is the Perpetual Black’s version of night. During this time, an ink-like fog seems to cover the known world, enveloping all of its inhabitants and rendering them unable to see further then 2 feet away from themselves. At first, it starts by rising up from the ground extremely slowly. Once it reaches 1 foot thick, people are barely able to see where they are placing their feet. It rises achingly slow until it reaches a point to where it seems to reach into the sky.
The orgins of this are unknown. In fact, this phenomenon has been occuring for so long, that the inhabitants of the world have adapted to it, and all of recorded history includes it. To the players, this effect will seem unnatural; however, to the people living there, its just a part of life. With that in mind, the entire world revolves around it and moves at its pace.
To be exact, the ink begins to rise at 5pm and raises 2 foot per hour until 10, where it suddenly accelerates to 10 foot per hour at first but then fills up even faster later on (People have tried building a tower to see over top of it, all attempts have failed). It begins to drop once more at an extremely high rate at 2 am and is almost entirely gone at 5am.
For the players, imagine what it would be like at the depths of the ocean without light. Light sources during this time are not snuffed out entirely; however, they are choked down to a tiny portion of what they previously were, this includes spells. The reason for this is simply because light seems to reflect off of it. So, in the case of torches, since the fire eats it up in the area that its in, beyond that area all the light is reflected back in on itself with little to no penetration.
This effect also happens to sound which seems to be reflected back on its source with very little penetration. So, if you are in a room with someone else, you can hear them step, but it would sound like it came from roughly 17 sources at the same time in random directions at varying degrees. Telepathy falls under a similar effect though it the reason for this is unknown.
For all purposes, it is virtually impossible for a normal person to find someone without prior knowledge of their position. See more in the rulings section for what you can do to navigate in the Ink.